The present invention relates to an installable load shoulder for a wellhead, a method for installing a load shoulder in a wellhead, and a system for supporting tubing in a wellhead.
Load shoulders to support tubing hangers in a wellhead system may be installed by welding the load shoulder to the wellhead, or a load shoulder may be installed in a groove in a wellhead.
In some drilling programs, wellhead, or wellhead systems, must be capable of supporting heavy, lengthy tubing. “Tubing” or “tubing string” as used herein and in the claims is meant to be inclusive of any tubular product used in drilling and completing oil or gas wells, and is particularly inclusive of casing and production tubing. When a borehole in the earth is completed, it is customary to attach to the upper end of the well structure a wellhead, comprised of one or more wellhead members, which provide the superstructure for supporting concentrically arranged smaller diameter tubular strings. As an example, a common expedient is to suspend within a casing string, a tubing string and testing equipment that is supported by a wellhead. For this purpose it is traditional to employ a tubing hanger that is secured to a length of tubing and accordingly structure must be provided to support the tubing hanger to, or within, the wellhead. The term “tubing hanger” as used herein and in the claims is meant to be inclusive of any hanger member adapted to support a tubing, particularly including a tubing hanger, a casing hanger, a slip hanger and a mandrel.
U.S. Pat. No. 5,984,008 issued Nov. 16, 1999 to Lang et al., describes an installable load shoulder formed as a toroidal member having a split therein and a plurality of vertical openings and slots formed in the member to impart flexibility for installation. The installable load shoulder is received in a circumferential groove formed in the bore of a wellhead and functions to support a tubing hanger which in turn supports a length of tubing. This type of installable load shoulder acts somewhat like a spring to allow it to flex as it is installed through a smaller diameter vertical bore of the wellhead, but then spring outwardly into the larger diameter circumferential groove. This type of installable load shoulder is well suited for relatively low loads, limiting its applicability for higher load applications involving longer tubing strings.
U.S. Pat. No. 6,484,382 issued Nov. 26, 2002 to Smith describes the manufacture of an installable segmented load shoulder and a wellhead for same. The assembled load shoulder segments are supported in a circumferential groove formed in the bore of a wellhead. Set screws or a pin are used to secure the load shoulder to the wellhead. The segments allow the load shoulder to be stepwise installed through the smaller diameter vertical bore of the wellhead. As well, the segments allow the load shoulder to be formed from higher strength steel to support higher loads.